So-called composing scanners, which can reproduce images of desired areas of plural originals, have recently become practical. Such scanners also reproduce images arranged as desired, at desired magnifications. U.S. pat. application Ser. No. 625,782 now U.S. Pat. No. 4,684,979 and Japanese Patent Application No. 58-144742, for example, describe how scanning systems of this type reproduce points of an original precisely onto corresponding points of a reproduction image. However, in this type of scanning system, it is necessary to determine a specific point, for example, a beginning or an ending scan point, for each original positioned on the original scanning drum. Moreover, if originals are to be positioned obliquely, this type of system requires a special device for that purpose, such as the one disclosed in the Japanese Patent Publication No. 54-100802.
Japanese Patent Publication No. 58-90640 discloses one method for eliminating such inconveniences by projecting originals on a particular plane, e.g., that of a magnification measurer, obtaining coordinates of a specific point of each original image on that plane and determining the beginning points of a trimming process as well as other necessary points on the basis of those coordinates. However, to obtain arranged reproduction images on a photosensitive material by means of the composing scanner, it is necessary to position originals more efficiently on the original scanning drum.